Evidence for two mutually excluding temperatures in relativistic FE - Emulsion collisions

The concept of 'temperature' as a characteristic quantity describing measured momentum- and energy-distributions of observed particles is widely used in the analysis of hadron- nucleus collisions at medium and high energies. But describing an already rather small system like two colliding nuclei through such a number of subsystems, each with a well defined temperature, can induce some uneasiness as to the usefulness of this whole concept. On the other hand, it is not at all obvious that all these observed subsystems have to be realized in each individual collision. Different subsystems may well be formed in different collisions. This view is supported by the experience that in the authors' measured Fe - emulsion collisions at 1.8 AGeV there are two well defined and mutually excluding temperatures observable in such a way that in each individual collision only one of these temperatures is realized